Begin Exam Five material: Digestive System. Digestive System: Overview –mouth, pharynx, esophagus, stomach, small intestine, and large intestine –teeth,

Begin Exam Five material: Digestive System

Digestive System: Overview

• – mouth, pharynx,

esophagus, stomach, small intestine, and large intestine

• – teeth, tongue,

gallbladder, salivary glands, liver, and pancreas

Digestive Process

• The GI tract is a _____________________________________ line – Nutrients become more available to the body in each

step

• There are six essential activities: – Ingestion – – mechanical digestion – – – defecation

G.I. Tract Activities

• Ingestion –

• Propulsion – swallowing and peristalsis– Peristalsis –

______________________ of muscles in the organ walls

• Mechanical digestion –

Gastrointestinal Tract Activities

• Chemical digestion– catabolic _

• – movement of nutrients _

• Defecation– elimination of _

GI Tract

• ___________________________________ for the digestive process

• Regulation of digestion involves:– Mechanical and chemical stimuli –

_________________________________, osmolarity, and presence of substrate in the lumen

– Extrinsic control by _

– Intrinsic control by _

Receptors of the GI Tract

• Mechano- and chemoreceptors respond to:– Stretch, osmolarity, and pH– Presence of substrate, and end products of

digestion• They initiate reflexes that:

–

–

Nervous Control of the GI Tract

• Intrinsic controls– ______________________________________

initiate short reflexes– Short reflexes are mediated by local enteric

plexuses (gut brain)• Extrinsic controls

– Long reflexes arising within or outside the GI tract

– ____________________________ and extrinsic _

Peritoneum and Peritoneal Cavity

• Peritoneum – ______________________________________

of the abdominal cavity–

• covers external surface of most _–

• lines the _

• Peritoneal cavity– ________________________________

digestive organs – Allows them to slide across one another

Peritoneum and Peritoneal Cavity

• Mesentery :

– supplies _____________________________ to the viscera

– Holds digestive organs in place and _

Histology of the Alimentary Canal

• From esophagus to the anal canal the walls of the GI tract have the _

– From the lumen outward they are the _________________________, _________________________, muscularis externa, and ___________________________

• Each tunic has a predominant tissue type and a specific digestive function

Figure 23.6

Mucosa

• Moist epithelial layer that _____________________________ of the alimentary canal

• Three major functions:– – – _______________________________ against

infectious disease• Consists of three layers: a lining epithelium,

lamina propria, and muscularis mucosae

Mucosa: Epithelial Lining

• ________________________________ and mucus-secreting goblet cells

• Mucus secretions:– _______________________________________

from digesting themselves– Ease food along the tract

• Stomach and small intestine mucosa contain:–

– __________________________________ -secreting cells (making them endocrine and digestive organs)

Mucosa: Lamina Propria and Muscularis Mucosae

• – Nourishes the epithelium and absorbs

nutrients– Contains lymph nodes

_____________________________ important in defense against bacteria

• Muscularis mucosae – __________________________________

that produce local movements of mucosa

Mucosa: Other Sublayers

• – dense connective tissue containing elastic fibers, blood

and lymphatic vessels, lymph nodes, and nerves

• Muscularis externa – responsible for _

• Serosa – the _– Replaced by the fibrous adventitia in the esophagus – Retroperitoneal organs have both an adventitia and

serosa

Enteric Nervous System

• two major intrinsic nerve plexuses:•

– regulates glands and smooth muscle in the mucosa

• _____________________________ – Major nerve supply that controls GI tract mobility

Enteric Nervous System

• Segmentation and peristalsis are largely ______________________________ involving local reflex arcs

• Linked to the CNS via long _____________________________ reflex arc

Mouth

• Oral or _____________________ cavity:– Is bounded by lips, cheeks, palate, and

tongue –oral orifice

• –continuous with the oropharynx

posteriorly

Mouth

• To withstand _

– The mouth is lined with _

– The gums, hard palate, and dorsum of the tongue are _

Lips and Cheeks• Have a core of skeletal muscles

–Lips: –Cheeks:

• – bounded by the lips and cheeks

externally, and teeth and gums internally

Lips and Cheeks

• Oral cavity proper –area that lies _

• –median fold that joins the internal aspect

of each lip to the gum

Palate

• Hard palate – palatine bones and palatine processes of

the maxillae

–

– Slightly _________________________ on either side of the raphe (midline ridge)

Palate

• Soft palate – mobile fold _

–Closes off the nasopharynx during swallowing

–

Tongue

• Occupies the _• fills the oral cavity when mouth is closed

• Functions include:– ____________________________________

food during chewing– ____________________________________

_ and forming the bolus– Initiation of _

Tongue

• ______________________________ muscles change the _

• _______________________________ muscles alter the tongue’s _

• ___________________________________ secures the tongue to the floor of the mouth

Tongue

• three types of papillae–

• give the tongue roughness and provide friction

– • scattered widely over the tongue and give

it a reddish hue–

• V-shaped row in back of tongue

Tongue

• – groove that separates the tongue into two

areas:

– Anterior 2/3 residing in the _

– Posterior third residing in the _

Tongue

Figure 23.8

Salivary Glands

• Produce and secrete saliva that: – –Moistens and dissolves food chemicals –Aids in bolus formation–Contains _

Salivary Glands

• Three pairs of ____________________ glands – – –

• Intrinsic salivary glands (_______________________ glands) – scattered throughout the oral mucosa

Salivary Glands• Parotid

– lies _______________________________ between the masseter muscle and skin

– _________________________________ opens into the vestibule next to second upper molar

• Submandibular – lies along the medial aspect of the

mandibular body– ducts open at the _

Salivary Glands

• Sublingual – lies anterior to the submandibular gland _

– It opens via 10-12 ducts into the _

Salivary Glands

Figure 23.9a

Saliva: Source and Composition

• Secreted from ________________________ cells of salivary glands

• contains– _______________________________ – Na+, K+, Cl–,

PO42–, HCO3

–

– Digestive enzyme –

– Proteins – mucin, lysozyme, defensins, and IgA– ____________________________________ – urea

and uric acid

Control of Salivation

• Intrinsic glands keep the mouth _• Extrinsic salivary glands secrete serous,

enzyme-rich saliva in response to: – Ingested food which stimulates

chemoreceptors and pressoreceptors – The thought of food

• Strong ________________________________ inhibits salivation and results in dry mouth

Teeth• Primary

– __________________________________ that erupt at intervals between 6 and 24 months

• Permanent – enlarge and develop causing the root of

deciduous teeth to be resorbed – fall out between the ages of _– All but the third molars have erupted by the

end of adolescence– Usually _

Classification of Teeth

• Based on shape and function•

– chisel-shaped teeth for cutting or nipping• Canines

– fanglike teeth that _• Premolars (bicuspids) and molars

– have _______________________________; best suited for grinding or crushing

Tooth Structure• Two main regions – • Crown

– ______________________________ above the gingiva

• Enamel – acellular, brittle material composed of calcium

salts and hydroxyapatite crystals; – –

• Root – portion of the tooth _

Tooth Structure

• Neck – constriction _

• Cementum – – –Attaches it to the periodontal ligament

Tooth Structure

• Periodontal ligament–________________________________

in the alveolus of the jaw

–Forms the _• Gingival sulcus

–depression where the gingiva borders the tooth

Tooth Structure

• Dentin –bonelike material

________________________________ that forms the bulk of the tooth

• – cavity surrounded by dentin that

contains pulp • Pulp

–connective tissue, _

Tooth Structure

• Root canal –portion of the pulp cavity that extends

into the root

• Odontoblasts –secrete and maintain dentin throughout

life

Tooth and Gum Disease• Dental _

– gradual ___________________________ of enamel and dentin by bacterial action

– Dental plaque adheres to teeth• a film of _

– Acid from the bacteria dissolves calcium salts– Without calcium salts, organic matter is

digested by _– Daily flossing and brushing help prevent

caries by removing forming plaque

Tooth and Gum Disease: Periodontitis

• Gingivitis –as plaque accumulates, it _

• Accumulation of calculus:–________________________________

between the gingivae and the teeth

–Puts the gums at risk for infection

Tooth and Gum Disease: Periodontitis

• Periodontitis – serious gum disease resulting from an _

• Immune system attacks intruders as well as body tissues, _

Pharynx• From the mouth, the oro- and

laryngopharynx allow passage of:– Food and fluids to the _

– ________________________ to the trachea

• Lined with _________________________ epithelium and _

Esophagus

• _____________________________ going from the laryngopharynx to the stomach

• Travels through the _

• Joins the stomach at the cardiac orifice

Esophageal Characteristics

• Esophageal mucosa – nonkeratinized stratified squamous epithelium

• Glands secrete mucus as a____________ moves through the esophagus

• Muscle changes from ______________________ (superiorly) to ______________________ (inferiorly)

Digestive Processes in the Mouth

• Food is ingested

• ________________________ digestion begins (chewing)

• _____________________________ is initiated by swallowing

• _________________________________ begins chemical breakdown of starch

Deglutition (Swallowing)

• Coordinated activity of the tongue, soft palate, pharynx, esophagus, and 22 separate muscle groups

• – bolus is forced into the _

Deglutition (Swallowing)•

– controlled by the _

– All routes except into the digestive tract are sealed off

• Peristalsis moves food through the pharynx to the esophagus

Figure 23.13

(d) (e)

Relaxedmuscles

Circular musclescontract,constrictingpassagewayand pushingbolus down

Bolus offoodLongitudinalmusclescontract,shorteningpassagewayahead of bolus

Gastroesophagealsphincter closed

Stomach

Relaxedmuscles

Gastroesophagealsphincter open

(a) (b) (c)

Tongue

Trachea

Pharynx

Epiglottis

Glottis

Upper esophagealsphincter contracted

Bolus of food

Upper esophagealsphincter relaxed

Epiglottis

Esophagus

Uvula

Bolus

Bolus

Upper esophagealsphincter contracted

Stomach• Chemical breakdown of ___________________

and food is _•

– surrounds the cardiac orifice•

– dome-shaped region beneath the diaphragm•

– midportion of the stomach•

– made up of the antrum and canal which terminates at the pylorus

– The pylorus is __________________________________________ through the pyloric sphincter

Stomach

• Greater curvature – entire extent of the _

• Lesser curvature – concave _

• Lesser omentum – runs from the _

• Greater omentum – drapes inferiorly from the _

Stomach

• – sympathetic and parasympathetic fibers of the

autonomic nervous system

• Blood supply – _______________________________, and

corresponding veins (part of the hepatic portal system)

Figure 23.14a

Microscopic Anatomy of the Stomach

• Epithelial lining is composed of:– ____________________________ that

produce a coat of alkaline mucus• The mucous surface layer traps a bicarbonate-rich

fluid beneath it

• ________________________ contain gastric glands that secrete _

Anatomy of the Stomach

Figure 23.15a

Microscopic Anatomy of

the Stomach

Figure 23.15c

Glands of the Stomach Fundus and Body

• Gastric glands of the fundus and body have a variety of secretory cells

– • secrete _

– Parietal cells•

Glands of the Stomach Fundus and Body

– Chief cells • produce _• Pepsinogen is activated to pepsin by:

– – __________________________________ itself via a

positive feedback mechanism

– Enteroendocrine cells • secrete gastrin, histamine, endorphins, serotonin,

cholecystokinin (CCK), and somatostatin into the lamina propria

Digestion in the Stomach

• The stomach:– ______________ ingested food– Degrades this food both physically and

chemically– ____________________________ to the

small intestine– Enzymatically _

– Secretes ______________________________ required for absorption of vitamin B12

Regulation of Gastric Secretion

• release of gastric juices–_________________________ (reflex)

phase: • prior to food entry

–_________________________ phase: • once food enters the stomach

–__________________________ phase: • as partially digested food enters the

duodenum

Cephalic Phase

• Excitatory events include:– – Stimulation of taste or smell receptors

• Inhibitory events include:– Loss of appetite or _– ____________________________ in

stimulation of the _

Gastric Phase

• Excitatory events include:–

– Activation of stretch receptors

– Activation of ____________________________ by peptides, caffeine, and rising pH

– Release of ____________________________ to the blood

Gastric Phase

• Inhibitory events include:

– A pH _

– ____________________________________ that overrides the parasympathetic division

Intestinal Phase• Excitatory phase

– low pH; partially digested food enters the duodenum and _

• Inhibitory phase – distension of duodenum,

__________________________________, acidic, or hypertonic chyme, and/or irritants in the duodenum

– Closes the _– Releases hormones that _

Regulation and Mechanism of HCl Secretion

• HCl secretion is stimulated by – – – _______________________________

through second-messenger systems

• Antihistamines block H2 receptors and _

Response of the Stomach to Filling

• Reflex-mediated events include:–

• as food travels in the esophagus, stomach muscles relax

– • the stomach dilates in response to gastric filling

• Plasticity – the ability to be _

Gastric Contractile Activity

• Most vigorous peristalsis and mixing occurs near the pylorus

• Chyme is either:– Delivered in _

or

– Forced ________________________________ for further mixing

Regulation of Gastric Emptying

• Gastric emptying is regulated by:

– The neural _

– Hormonal (enterogastrone) mechanisms

• These mechanisms _______________________________ and duodenal filling

Regulation of Gastric Emptying

• ______________________-rich chyme – ____________________________ moves

through the duodenum

• _________________-laden chyme – digested ___________________________

causing food to remain in the stomach longer

Small Intestine: Gross Anatomy

• Runs from pyloric sphincter to the ileocecal valve

• Has three subdivisions:

• • •

Small Intestine: Gross Anatomy

• The _– Join the duodenum at the hepatopancreatic

ampulla – Are controlled by the _

• The jejunum extends from the duodenum to the ileum

• The ileum joins the large intestine at the __

Small Intestine: Microscopic Anatomy

• Structural modifications of the small intestine wall increase surface area– Plicae circulares: deep

__________________________ of the mucosa and submucosa

– Villi• fingerlike _

– • tiny projections of absorptive mucosal cells’ plasma

membranes

Duodenum and Related Organs

Figure 23.20

Figure 23.21

Small Intestine: Histology of the Wall

• Cells of ___________________________ secrete intestinal juice

• _______________________________ are found in the submucosa

• Brunner’s glands in the duodenum secrete _

Intestinal Juice

• Secreted by intestinal glands _

• Slightly alkaline

• Largely water, – enzyme-poor, but _

Liver

• The _________________________ in the body

• Superficially has _ – right, left, caudate, and quadrate

• The _– Is a remnant of the fetal _

Liver: Associated Structures

• The lesser omentum _

• The ______________________________ rests in a recess on the inferior surface of the right lobe

Liver: Associated Structures

• Bile leaves the liver via:– Bile ducts,

• which fuse into the common hepatic duct

– The common hepatic duct, • which fuses with the cystic duct

• ___________________________________ form the bile duct

Composition of Bile• A yellow-green, alkaline solution containing

– – – – neutral fats, – phospholipids, – electrolytes

• Bile salts are cholesterol derivatives that:– – Facilitate fat and cholesterol absorption– Help solubilize cholesterol

Bile

• Enterohepatic circulation _

• The chief bile ______________________ is bilirubin– waste product of _

The Gallbladder

• Thin-walled, green ___________________________ on the ventral surface of the liver

• • •

– via the cystic duct– flows into the bile duct

Regulation of Bile Release

• Acidic, _________________________ causes the duodenum to release:

– Cholecystokinin (CCK)

–

– into the _

Regulation of Bile Release

• Cholecystokinin causes:

– The _

– The hepatopancreatic _

• As a result, bile _

Figure 23.25

Acidic, fatty chyme entering duodenum causesrelease of cholecystokinin and secretin from duodenal wallenteroendocrine cells

Cholecystokinin and secretin enter the bloodstream

Cholecystokinin(via bloodstream)causes gallbladderto contract andhepatopancreaticsphincter to relax;bile entersduodenum

Bile saltsand secretintransported viabloodstreamstimulate liverto produce bilemore rapidly

Bile salts reabsorbed into blood

Vagal stimulation causesweak contractions of gallbladder

1

2

6

5

4

3

Pancreas

• Location– Lies deep to the greater curvature of the

stomach

– The _______________________________________ and the tail is near _

Pancreas

• Exocrine function– – Acini (clusters of secretory cells) contain

_________________________________ with digestive enzymes

• The pancreas also has an _ – release of _

Composition and Function of Pancreatic Juice

• Water solution of _ (primarily HCO3

–)– ___________________________ acid chyme– Provides

_______________________________ for pancreatic enzymes

• Enzymes are released in _______________________________ and activated in the duodenum

Composition and Function of Pancreatic Juice

• Examples include– __________________________ is activated

to trypsin– Procarboxypeptidase is activated to _

• Active enzymes secreted– Amylase, lipases, and nucleases – These enzymes require

___________________ for optimal activity

Regulation of Pancreatic Secretion

• CCK and secretin enter the bloodstream when fatty or acidic chyme enters the duodenum

• Upon reaching the _– CCK causes secretion

• – Secretin causes secretion

•

• Vagal stimulation also causes release of pancreatic juice

Regulation of Pancreatic Secretion

Figure 23.28

Acidic chyme enteringduodenum causes theenteroendocrine cells ofthe duodenal wall to releasesecretin, whereas fatty,protein-rich chyme inducesrelease of cholecystokinin.

During cephalic and gastricphases, stimulation byvagal nerve fibers causesrelease of pancreatic juiceand weak contractions ofthe gallbladder.

Upon reaching thepancreas, cholecystokinininduces the secretion ofenzyme-rich pancreatic juice;secretin causes copioussecretion of bicarbonate-richpancreatic juice.

Cholecystokininand secretin enterbloodstream.

1

2

3

Digestion in the Small Intestine

• As chyme enters the duodenum:

– Carbohydrates and proteins are only partially digested

–

Digestion in the Small Intestine

• Digestion continues in the small intestine– Chyme is ____________________________

into the duodenum – Because it is hypertonic and has low pH, _

– Virtually ____________________________________ takes place in the small intestine

Motility in the Small Intestine

• The most common motion of the small intestine is _

– It is initiated by _

(Cajal cells)

– Moves contents steadily toward the _

Motility in the Small Intestine

• After nutrients have been absorbed:

– Peristalsis begins with each wave starting distal to the previous

– Meal remnants, bacteria, mucosal cells, and debris are _

Control of Motility

• Local enteric neurons of the GI tract coordinate intestinal motility

• _________________________________ cause:– Contraction and shortening of the _

– Shortening of _– Distension of the intestine

Control of Motility

• Other impulses relax the circular muscle

• The

– Relax the _

– Allow chyme to pass into the large intestine

Large Intestine

• Has three unique features:–

• three bands of longitudinal smooth muscle in its muscularis

– • pocketlike sacs caused by the tone of the teniae

coli

– Epiploic appendages •

Large Intestine

• Is subdivided into the – – – – –

• The saclike cecum:– Lies below the ileocecal valve in the right iliac fossa– Contains a wormlike vermiform appendix

Figure 23.29a

Colon

• Has distinct regions: ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, and sigmoid colon

• The _________________________ joins the _

• The _____________________________ opens to the exterior _

Sphincters of the Anus

• The anus has ____________ sphincters:– __________________ anal sphincter

• composed of _________________________ muscle

– __________________ anal sphincter • composed of _________________________

muscle

• These sphincters are closed _

Large Intestine: Microscopic Anatomy

• Colon mucosa is _____________________________ epithelium except in the anal canal

• Has numerous deep ________________ lined with _

Large Intestine: Microscopic Anatomy

• Anal canal mucosa is _

• Anal sinuses _

• Superficial venous plexuses are associated with the anal canal

• Inflammation of these veins results in itchy varicosities called _

Structure of the Anal Canal

Figure 23.29b

Bacterial Flora• The _______________________ of the

large intestine consist of:– Bacteria surviving the small intestine that

enter the cecum and – Those entering via the anus

• These bacteria: – – Release irritating acids and _– Synthesize ___________________________

and vitamin K

Functions of the Large Intestine

• Other than digestion of enteric bacteria, _

• Vitamins, water, and electrolytes _

• Its major function is _________________________________ toward the anus

• Though essential for comfort, the colon is _

Motility of the Large Intestine

• – Slow segmenting movements that move the

contents of the colon– contract as they are _

• Presence of _– Activates the _– Initiates peristalsis that _

Defecation

• _____________________ of rectal walls caused by feces:– _____________________________ of the rectal

walls– Relaxes the ________________ anal sphincter

• Voluntary signals stimulate relaxation of the external anal sphincter and defecation occurs

Chemical Digestion: Carbohydrates

• Absorption: – Enter the _– Transported to the ____________via the

_______________________________• Enzymes used:

– _______________________ amylase, – _______________________ amylase, –

Chemical Digestion: Proteins

• Absorption: similar to carbohydrates• Enzymes in the stomach

– • Enzymes in the _

– _______________________________ – trypsin, chymotrypsin, and carboxypeptidase

– _______________________________ – aminopeptidases, carboxypeptidases, and dipeptidases

Chemical Digestion: Fats

• Absorption: Diffusion into intestinal cells where they:–

– Enter __________________________ and are transported to systemic circulation _

Chemical Digestion: Fats

• Glycerol and short chain fatty acids are:– Absorbed into the _– Transported via the _

• Enzymes/chemicals used: – bile salts –

Chemical Digestion: Nucleic Acids

• Absorption: ______________________ via membrane carriers

• Absorbed in villi • transported to liver via hepatic portal vein• Enzymes used:

– pancreatic ribonucleases and deoxyribonuclease in the small intestines

Malabsorption of Nutrients

• Results from anything that – interferes with _

– ______________________________ the intestinal mucosa (e.g., bacterial infection)

Malabsorption of Nutrients

• Gluten enteropathy _

– _________________________ damages the intestinal villi

– reduces the _

• Treated by eliminating gluten from the diet (all grains but rice and corn)

Cancer

• Stomach and colon cancers _________________________________ or symptoms

• Metastasized _____________________ frequently cause _

• Prevention is by regular dental and medical examinations

Cancer

• _____________________________ is the 2nd largest cause of cancer deaths in males – (__________________________ is 1st)

• Forms from benign mucosal tumors – – formation increases with age

• Regular colon examination should be done for _

Kidney Functions

• Filter 200 liters ________________ daily, allowing toxins, metabolic wastes, and excess ions to leave the body in urine

• _____________________________ and chemical makeup of the blood

• Maintain the _____________________ between water and salts, and acids and bases

Other Renal Functions

• ____________________________ during prolonged fasting

• Production of __________________ to help ____________________________ and ______________________________ to stimulate _______________ production

• Activation of vitamin D

Other Urinary System Organs

• – provides a temporary storage reservoir for

urine• Paired ureters

– transport urine from _

• Urethra – transports urine from the _

Figure 25.1a

Layers of Tissue Supporting the Kidney

• – fibrous capsule that prevents kidney infection

• Adipose capsule – _______________________ that cushions the kidney

and helps _________________ to the body wall

• Renal fascia – outer layer of ________________________________

that anchors the kidney

Kidney Location and External Anatomy

Figure 25.2a

Internal Anatomy (Frontal Section)

• – the light colored, __________________________

superficial region• Medulla

– exhibits cone-shaped _________________________ separated by columns

– The medullary pyramid and its surrounding capsule constitute a lobe

• – flat funnel shaped tube lateral to the hilus within the

renal sinus

Internal Anatomy

• Major calyces– large ______________________________ of

the renal pelvis– _____________________________ draining

from papillae – Empty urine into the pelvis

• Urine flows through the _

Figure 25.3b

Renal Vascular Pathway

Figure 25.3c

The Nephron

• ________________________ are the structural and functional units that form urine, consisting of:– Glomerulus

• a tuft of ________________________________ associated with a _

– Glomerular (Bowman’s) capsule • blind, ___________________________________

that completely surrounds the glomerulus

The Nephron

–Renal _• the glomerulus and its Bowman’s capsule

– • ______________________ epithelium that

allows solute-rich, _________________________________ to pass from the blood into the glomerular capsule

Renal Tubule

• Proximal convoluted tubule (PCT) ––composed of cuboidal cells with

numerous _

–____________________________ and solutes from filtrate and secretes substances into it

Renal Tubule

• – a hairpin-shaped loop of the renal tubule

• Distal convoluted tubule (DCT)– cuboidal cells without microvilli that _

Figure 25.4b

Nephrons

• – 85% of nephrons; located in the cortex

• Juxtamedullary nephrons:– Are located at the cortex-medulla junction– Have loops of Henle that _

– Are involved in the production of _

Figure 25.5a

Capillary Beds of the Nephron

• Every nephron has _________ capillary beds– –

• Each glomerulus is: – Fed by an _ – Drained by an _

Capillary Beds of the Nephron

• Blood pressure in the glomerulus is high because:– Arterioles are high-resistance vessels– Afferent arterioles _____________________

than efferent arterioles

• Fluids and solutes are forced out of the blood throughout the entire length of the glomerulus

Capillary Beds

• Peritubular beds are _____________________, porous capillaries ____________________ that: – Arise from efferent arterioles– Cling to adjacent renal tubules– Empty into the renal venous system

• Vasa recta – long, straight _

Juxtaglomerular Apparatus (JGA)

• Where the distal tubule lies against the afferent (sometimes efferent) arteriole

• Arteriole walls have juxtaglomerular (JG) cells– Enlarged, _

– Have _

– Act as _

Juxtaglomerular Apparatus (JGA)

• – Tall, closely packed distal tubule cells – Lie adjacent to _– Function as chemoreceptors or

osmoreceptors• Mesanglial cells:

– Have ______________________________ properties

– Influence capillary _

Juxtaglomerular Apparatus (JGA)

Figure 25.6

Mechanisms of Urine Formation

• The kidneys filter the body’s _

• The filtrate:– Contains all plasma components _– Loses water, nutrients, and essential ions to

become urine• The urine contains _

Mechanisms of Urine Formation

• Urine formation and adjustment of blood composition involves three major processes –

–

–

Figure 25.8

Glomerular Filtration

• The _________________________ is more efficient than other capillary beds because:– Its filtration membrane is _

– Glomerular _

– It has a higher _

Glomerular Filtration Rate (GFR)

• The total amount of filtrate formed per minute by the kidneys

• Factors governing filtration rate at the capillary bed are:– Total _________________________

available for filtration– Filtration membrane _–

Glomerular Filtration Rate (GFR)

• GFR is ___________________________ to the NFP

• Changes in GFR normally result from changes in _

Glomerular Filtration Rate (GFR)

Figure 25.9

Regulation of Glomerular Filtration

• If the GFR is too high:– Needed substances _

• If the GFR is too low:– ____________________________________,

including wastes that are normally disposed of

Regulation of Glomerular Filtration

• Three mechanisms control the GFR

– Renal autoregulation _

– Neural controls

– Hormonal mechanism (the __________________________________ system)

Intrinsic Controls

• Under normal conditions, renal autoregulation maintains a _____________________________ glomerular filtration rate

Extrinsic Controls

• When the _________________________ nervous system is at ________________:

– Renal blood vessels are _

– Autoregulation mechanisms prevail

Extrinsic Controls• Under stress:

– _______________________ is released by the sympathetic nervous system

– _______________________ is released by the _

– ___________________________________ and filtration is inhibited

• The sympathetic nervous system also stimulates the renin-angiotensin mechanism

Renin-Angiotensin Mechanism

• Is triggered when the JG cells release renin• Renin acts on ___________________________

to release _• Angiotensin I is converted to angiotensin_• Angiotensin II:

– Causes mean _ – Stimulates the adrenal cortex to release _

• As a result, both systemic and glomerular hydrostatic pressure rise

Renin Release

• Renin release is triggered by:– ___________________________ of the

granular JG cells

– Stimulation of the JG cells by _

– Direct stimulation of the JG cells by _

– Angiotensin _

Tubular Reabsorption

• All ______________________________ are reabsorbed

• Water and ion reabsorption is _________________________ controlled

• Reabsorption may be an active (requiring ATP) or passive process

Nonreabsorbed Substances

• A ___________________________ (Tm): – Reflects the number of _______________ in

the renal tubules available – Exists for nearly every substance _

• When the carriers are ______________________, excess of that substance _

Nonreabsorbed Substances

• Substances are not reabsorbed if they: – – Are _– Are too large to pass through membrane

pores

• Urea, creatinine, and uric acid are the most important nonreabsorbed substances

Atrial Natriuretic Peptide Activity• ANP _

– _________________________ blood volume– Lowers blood pressure

• ANP lowers blood Na+ by:– Acting directly on medullary ducts to _– Counteracting the effects of _– Indirectly stimulating an increase in GFR

reducing water reabsorption

Tubular Secretion

• Essentially reabsorption in reverse, – substances move from peritubular capillaries

or tubule cells _• Tubular secretion is important for:

– Disposing of substances not already in the filtrate

– Eliminating undesirable substances such as _

– Ridding the body of excess _– Controlling blood _

Formation of Dilute Urine

• Filtrate is diluted in the ascending loop of Henle

• Dilute urine is created by allowing this filtrate to continue into the renal pelvis

• This will happen as long as _

Formation of Dilute Urine

• Collecting ducts remain _

– no further water reabsorption occurs

• Sodium and selected ions can be removed by active and passive mechanisms

Formation of Concentrated Urine

• Antidiuretic hormone (ADH) _

• This equalizes the osmolality of the filtrate and the interstitial fluid

• In the presence of ADH, _

Formation of Concentrated Urine

• ADH-dependent water reabsorption is called _

• ADH is the signal to produce _

• The kidneys’ ability to respond depends upon the high medullary osmotic gradient

Diuretics

• Chemicals that enhance the urinary output include:– Any substance _

– Substances that exceed the ability of the renal tubules to reabsorb it

– Substances that _

Diuretics

• Osmotic diuretics include:– High _

• carries water out with the glucose – Alcohol

• – Caffeine and most diuretic drugs

• – _______________________ and Diuril

• inhibit Na+-associated symporters

Ureters

• Slender tubes that _

• Ureters enter the _

– This closes their distal ends as bladder pressure increases and prevents backflow of urine into the ureters

Ureters

• Ureters have a _– Transitional epithelial mucosa– Smooth muscle muscularis– Fibrous connective tissue adventitia

• Ureters ___________________________ via response to smooth muscle stretch

Urinary Bladder• Smooth, collapsible, muscular sac that stores

urine• It lies retroperitoneally on the pelvic floor _

– Males •

– Females•

• – triangular area outlined by the openings for the ureters

and the urethra– Clinically important because _

Urinary Bladder

• The bladder wall has three layers – – A _– A _

• The bladder is distensible and collapses when empty

• As urine accumulates, the bladder expands without significant rise in internal pressure

Urinary Bladder

Urethra

• Muscular tube that:

– Drains _

– Conveys it out of the body

Urethra

• Sphincters keep the urethra closed when urine is not being passed– ____________________ urethral sphincter

• __________________________ sphincter at the bladder-urethra junction

– ____________________ urethral sphincter • __________________________ sphincter

surrounding the urethra as it passes through the urogenital diaphragm

– Levator ani muscle •

Urethra• The female urethra is _• Its external opening lies _

• The male urethra has three named regions– Prostatic urethra

•

– Membranous urethra• runs through _

– • passes through the penis and opens via the _

Micturition (Voiding or Urination)• The act of emptying the bladder• Distension of bladder walls initiates spinal

reflexes that:– Stimulate contraction of the _– Inhibit the ____________________________

and internal sphincter (temporarily)• Voiding reflexes:

– Stimulate the _

– Inhibit the _